1. Field of the Invention
The invention relates to optical communications devices, such as transmitters, receivers, and transceivers used in high throughput fiber optic communications links in local and wide area networks and storage networks, and in particular to the communications protocol and packet format used by such devices, both for network communications and module management by monitoring and adapting the performance of such devices.
2. Description of the Related Art
Communications networks have experienced dramatic growth in data transmission traffic in recent years due to worldwide Internet access, e-mail, and e-commerce. As Internet usage grows to include transmission of larger data files, including content such as full motion video on-demand (including HDTV), multi-channel high quality audio, online video conferencing, image transfer, and other broadband applications, the delivery of such data will place a greater demand on available bandwidth. The bulk of this traffic is already routed through the optical networking infrastructure used by local and long distance carriers, as well as Internet service providers. Since optical fiber offers substantially greater bandwidth capacity, is less error prone, and is easier to administer than conventional copper wire technologies, it is not surprising to see increased deployment of optical fiber in data centers, storage area networks, and enterprise computer networks for short range network unit to network unit interconnection.
Such increased deployment has created a demand for electrical and optical transceiver modules that enable data system units such as computers, storage units, routers, and similar devices to be optionally coupled by either an electrical cable or an optical fiber to provide a high speed, short reach (less than 50 meters) data link within the data center.
A variety of optical transceiver modules are known in the art to provide such interconnection that include an optical transmit portion that converts an electrical signal into a modulated light beam that is coupled to a first optical fiber, and a receive portion that receives a second optical signal from a second optical fiber and converts it into an electrical signal, and similar implementations employ one fiber for both optical signals, traveling in opposite directions. The electrical signals are transferred in both directions over an electrical connectors that interface with the network unit using a standard electrical data link protocol.
The optical transmitter section of such transceiver modules includes one or more semiconductor lasers and an optical assembly to focus or direct the light from the lasers into an optical fiber, which in turn, is connected to a receptacle or connector on the transceiver to allow an external optical fiber to be connected thereto using a standard connector, such as SC, FC or LC. The semiconductor lasers are typically packaged in a hermetically sealed can or similar housing in order to protect the laser from humidity or other harsh environmental conditions. The semiconductor laser chip is typically a distributed feedback (DFB) laser with dimensions a few hundred microns to a couple of millimeters wide and 100-500 microns thick. The package in which they are mounted typically includes a heat sink or spreader, and has several electrical leads coming out of the package to provide power and signal inputs to the laser chips. The electrical leads are then soldered to the circuit board in the optical transceiver. The optical receive section includes an optical assembly to focus or direct the light from the optical fiber onto a photodetector, which in turn, is connected to a transimpedance amplifier/limiter circuit on a circuit board. The photodetector or photodiode it typically packaged in a hermetically sealed package in order to protect it from harsh environmental conditions. The photodiodes are semiconductor chips that are typically a few hundred microns to a couple of millimeters wide and 100 to 500 microns thick. The package in which they are mounted is typically from three to six millimeters in diameter, and two to five millimeters tall and has several electrical leads coming out of the package. These electrical leads are then soldered to the circuit board containing the amplifier/limiter and other circuits for processing the electrical signal.
Optical transceiver modules are therefore packaged in a number of standard form factors which are “hot pluggable” into a rack mounted line card network unit or the chassis of the data system unit. Standard form factors set forth in Multiple Source Agreements (MSAs) provide standardized dimensions and input/output interfaces that allow devices from different manufacturers to be used interchangeably. Some of the most popular MSAs include XENPAK (see www.xenpak.org), X2 (see www.X2msa.org), SFF (“small form factor”), SFP (“small form factor pluggable”), XFP (“10 Gigabit Small Form Factor Pluggable”, see www.XFPMSA.org), and the 300-pin module (see www.300pinmsa.org), and the QSFP (“Quad Small Form-factor Pluggable”, see www.qsfpmsa.org).
Customers and users of such modules are interested in small or miniaturized transceivers in order to increase the number of interconnections or port density associated with the network unit, such as, for example in rack mounted line cards, switch boxes, cabling patch panels, wiring closets, and computer I/O interfaces.
A variety of different optical and electrical communication protocols are in use, such as SONET, Gigabit Ethernet, 10 Gigabit Ethernet, Fibre Channel, and SDH optical protocols, and electrical interfaces such as Infiniband, XAUI, and XIF. Such variety complicates network management and the selection and specification of modules for individual links or applications.
Prior to the present invention, it has not been possible for a pluggable module to be used interchangeably with different optical and electrical protocols, or to adapt to different link or application requirements.
Another aspect of network management is that the length or nature of the link is sometimes reconfigured to accommodate different hubs or terminal end points, and with such network reconfiguration it is necessary to change the operational parameters or characteristics of the module. Some of these characteristics include laser power, wavelength, chirp, the communications packet, such as control field data, data rate, packet size, error correction methodology, or modulation technique.
Prior to the present invention, it has not been easily possible or practical to reconfigure a module to adjust such parameters.
The identification of individual modules in connection with adjusting such operating characteristics of such modules is an important consideration network management. When network conditions change, users must identify the specific components and reconfigure such components of the system.
Still another aspect of network management is module data analysis, to allow one to analyze the real time performances of an optical module in use, and observe error rates as a function of parametric shifts in performance. The information gained may be used in real time to reconfigure operational parametric shifts to achieve optimum product performance.
In the prior art, identification information, such as transceiver type, capability, serial number, compatibility information is known to be capable of being stored, in a transceiver (see, for example, U.S. Patent Application Publication 2003/0128411). However, prior to the present invention such information has not been readily accessible or easily or automatically utilized for adjusting operational parameters or the electrical or optical communications protocol of such individual modules in installations in the field during real time operation.